The present invention concerns new bis-pyrazole aza compounds, processes for making them and hair dye compositions containing these compounds.
There is an increasing demand for hair dye compositions that dye hair a copper color and chestnut brown to red shades as well as blond and brown to black colors. These requirements can of course be satisfied by oxidation hair dye preparations based on certain developer substances, such as p-aminophenol derivatives, and coupler substances, for example m-aminophenol or m-phenylenediamine derivatives. Addition of so-called direct-dyeing hair dye compounds is frequently required however to optimize the dye colors produced and to provide a uniform dyeing of the hair from the hair roots to the hair tips.
Addition of red dyes is necessarily required to produce brown shades in hair dye compositions that contain direct-dyeing hair dyes exclusively.
Previously nitro dye compounds have been almost exclusively used to attain this objective. There was a further need however for new direct-dyeing dye compounds that have excellent dye properties in the red range.